There is no cow level in World of Warcraft — at least that's what Blizzard wants you to believe. But you know better.

If you've been playing any of Blizzard's games — like Overwatch, Diablo 3 and Heroes of the Storm — you may have noticed there's a celebration underway in honor of Diablo's 20th anniversary. But there's a particularly cool event in World of Warcraft, Blizzard's iconic multiplayer online game.

World of Warcraft players recently discovered a secret level filled with demonic cows that you access by traveling through a magical portal. It's a reference to an old in-joke from the Diablo franchise about its hidden cow level Moo Moo Farm, the existence of which was repeatedly denied by the game's tooltips, according to GameSpot.

World of Warcraft Diablo 20th Anniversary Event: How to access the secret cow level

The first step to accessing the secret new level in World of Warcraft is finding and killing a treasure goblin — an enemy that first appeared in the Diablo series, according to Kotaku. According to a Reddit post from user Sindorein, these enemies show up in World of Warcraft as treasure chest icons on your mini map.

Treasure goblins should pop up "outdoors in the Broken Isles, in Legion dungeons of any difficulty and even in the Dalaran Sewers," according to Wowhead. Once you defeat one, a portal will open up that will take you to the secret cow level, as you can see in the GIF below.

Once you pass through the portal, you'll enter a farm area filled with evil, blood-thirsty cow enemies called "Diabolic Bovines."

The big boss at the end of this whole encounter is the Cow King, who will drop a special item when defeated, according to Wowhead. Using this item should grant you a special achievement in honor of Diablo's anniversary.

In addition to the Diablo-themed achievement, this secret cow level seems to drop some nice loot, so be sure to milk it for as long as you can. According to Wowhead, you can get the level's special loot once per day, per character. The event will run until Jan. 11.

More video game news, updates, tips and tricks

For more video game news, check out the latest from Mic. Here are the latest rumors on the potential internal storage issues with the Nintendo Switch, the latest rumors of a Terry Crews-voiced Overwatch character, video of a hilarious use for the jump pad on the new Overwatch map and the latest trailer for a beautiful puzzle game called Rime.